Dissolved oxygen micro-optrode belongs to the technology of one-dimensional microprobes for implementing measurement of a dissolved oxygen concentration at a certain point of submerged plant leaves. It is an optical fiber information exchange sensor based on the fluorescence quenching principle. As oxygen is the natural quenching agent for some fluorescent indicators, an oxygen-sensitive fluorescent indicator is made into an oxygen sensing film that is then coupled with an end portion of an optical fiber. High-brightness light-emitting diodes are adopted as a light source and a miniature photodiode test system. Then, oxygen concentrations can be determined according to optical fiber conducted florescence quenching intensities. Ruthenium complexes are applied most extensively so far because of their characteristics of insensitivity to stirring, inactivity to interferences of H2S, CO2 and salinity, and the like.
The existing method for detecting dissolved oxygen at the submerged plant leaf-water interface using the dissolved oxygen micro-optrode is to put submerged plant leaves to be tested in a test container first, then retain a dissolved oxygen detection probe to the top of the container, control a fluorescent probe on the dissolved oxygen detection probe to extend downwards until being positioned around the submerged plant leaves, and emit laser to the probe by the dissolved oxygen micro-optrode, thereby measuring the dissolved oxygen in water at the end portion of the probe under the fluorescence quenching principle.
The method has the following defects:
1. It fails in realizing in-situ measurement, and requires a submerged plant leaf sample for putting into the test container, which may easily cause a change to the natural environment around the submerged plant leaves, leading to inconsistency of the dissolved oxygen condition of the sampled submerged plant leaves with the actual condition.
2. Only one dissolved oxygen micro-optrode could be controlled each time to detect the dissolved oxygen condition at a certain level in a certain position of the submerged plant leaves, and for the submerged plant leaves, the dissolved oxygen conditions at other levels in the position can be obtained only through multiple measurement which, however, has a large span in time and fails in reflecting the actual conditions.
3. Single measurement can only be performed on one side of the submerged plant leaves, and the dissolved oxygen conditions on both front and back sides of the submerged plant leaves cannot be measured simultaneously.